gettap1.m

阵列信号处理的工具箱

function  wOut = gettap1(antenna, taperType, taperParam, scanDoa, wavelength)

%GETTAP1 Calculates tapering weights for array antennas.
%
%--------
%Synopsis:
%  wOut = gettap1(antenna, taperType, taperParam)
%
%Description:
%  Calculates tapering weights for for array antennas. The number of
%  elements is given via the "antenna" input parameter.
%
%Output and Input:
%  wOut  (CxVectorT): Tapering.
%  taperType [D](StringT): Type of taper.
%    = 'uniform' : Uniform taper, i.e. [1 1 ...].'. (default)
%    = 'taylor'  : Taylor tapering.
%    = 'taylor2' : Sampled continuous Taylor tapering.
%    = 'cheby'   : Dolhp-Chebychev tapering.
%    = 'user'    : User defined taper.
%  antenna (AntDefT): Antenna definition.
%  taperParam [D](): Taper parameter, see below.
%  scanDoa [D](DoaT): Pointing direction of the main beam. This adds extra
%    phase shifts to the tapering weights so that the main beam is scanned
%    in the desired direction.
%  wavelength (RealVectorT): Wavelength of the carrier [m].
%--------
%Uniform Taper Type.
%Synopsis:
%   wOut = gettap1(antenna, 'uniform')
%
%Description:
%
%--------
%Taylor Taper Type.
%Synopsis:
%  wOut = gettap1(antenna, 'taylor')
%  wOut = gettap1(antenna, 'taylor', SLL)
%  wOut = gettap1(antenna, 'taylor', [SLL nbar])
%
%Output and Input:
%  SLL   [D](RealScalarT): Sidelobe level SLL in dB (SLL > 0).
%  nbar [D](?): nbar. If nbar is given, also SLL must be given.
%
%Description:
%  Computes a Taylor taper with sidelobes SLL and parameter nbar.
%
%--------
%Taylor Taper Type 2.
%Synopsis:
%  wOut = gettap1(antenna, 'taylor2')
%  wOut = gettap1(antenna, 'taylor2', SLL)
%  wOut = gettap1(antenna, 'taylor2', [SLL nbar])
%
%Output and Input:
%  SLL [D](RealScalarT): Sidelobe level SLL in dB (SLL > 0).
%  nbar [D](?): nbar. If nbar is given, also SLL must be given.
%
%Description:
%  Computes a Taylor taper for a specified sidelobe level SLL>0.
%
%  This Taylor tapering is probably a sampled version of a continuous one.
%  The result will be good for a large antenna but worse for a small.
%  The error can be seen on the fact that the side lob closest to the main
%  beam is the smallest side lob. [5]
%
%Software Quality:
%  The function has been verified by comparing the results
%  with tables and plots in the following literature [2] fig. 3.6,
%  [3] fig. A.14. and [4] table 10.9.
%
%Known Bugs:
%  See the description above..
%
%--------
%Dolhp-Chebychev Taper Type.
%Synopsis:
%  wOut = gettap1(antenna, 'cheby')
%  wOut = gettap1(antenna, 'cheby', SLL)
%
%Output and Input:
%  SLL [D](RealScalarT): Sidelobe level SLL in dB (SLL > 0).
%  nbar [D](?): nbar. If nbar is given, also SLL must be given.
%
%Description:
%  Computes Dolhp-Chebychev taper weights of an n-element array with
%  sidelobes SLL. See [6], pp. 245-254.
%
%--------
%User Defined Taper Type.
%Synopsis:
%  wOut = gettap1(antenna, 'user', taper)
%
%Output and Input:
%  taper (CxVectorT): The tapering weights to use.
%
%Description:
%  Returns in input parameter "wOut" the tapering weights given by input
%  parameter "taper". In this way the user can use taperings that are not
%  supported by this function. One good reason to use this taper type is
%  to add phase shifts to the weights due to scanning the main beam of the
%  antenna in a desired direction.
%
%--------
%Notations:
%  Data type names are shown in parentheses and they start with a capital
%  letter and end with a capital T. Data type definitions can be found in [1]
%  or by "help dbtdata".
%  [D] = This parameter can be omitted and then a default value is used.
%  When the [D]-input parameter is not the last used in the call, it must be
%  given the value [], i.e. an empty matrix.
%  ... = There can be more parameters. They are explained under respective
%  metod or choice.
%
%Examples:
%
%Known Bugs:
%  Some functions that use this function can not supply the fourth input parameter
%
%References:
%  [1]: Bj鰎klund S.: "DBT, A MATLAB Toolbox for Radar Signal Processing.
%    Reference Guide", FOA-D--9x-00xxx-408--SE, To be published.
%  [2]: R.J.Mailloux, "Phased Array Antenna Handbook", 1994.
%  [3]: D.K.Barton, H.R.Ward,"Handbook of Radar Measurement, 1984.
%  [4]: M. Skolnik, "Radar Handbook", 2nd ed., 1990.
%  [5]: LP.
%  [6]: Balanis C.: "Antenna Theory, Analysis and Design", Wiley 1997, 
%    ISBN 0-471-59268-4.
%
%See Also:
%  defant, doaspc1, pantpat3, dbtdata

%   *  DBT, A Matlab Toolbox for Radar Signal Processing  *
% (c) FOA 1994-2000. See the file dbtright.m for copyright notice.
%
%  Start        : 970404 Svante Bj鰎klund (svabj).
%  Latest change: $Date: 2000/10/21 14:05:23 $ $Author: svabj $.
%  $Revision: 1.25 $
% *****************************************************************************


% ----------------------------------------------------------------------- %
% Handle standard input parameters
% ----------------------------------------------------------------------- %

if (nargin < 2)
  error('DBT-Error: To few input parameters.')
end

% ****************** Add missing input parameters ******************

if (nargin < 2)
  taperType = [];
end
if (nargin < 3)
  taperParam = [];
end
if (nargin < 4)
  scanDoa = [];
end


% ****************** Default values ******************
if (isempty(taperType))
  taperType = 'uniform';
end%if
if (isempty(scanDoa))
  scanDoa = [0;0];
end%if

% ****************** Error check input parameters ******************
chkdtype(taperType, 'StringT')
chkdtype(antenna, 'AntDefT')
chkdtype(scanDoa, 'DoaT')

antType = antenna.antennaType;

%if ~(strcmp(antType,'ULA') | strcmp(antType,'elem') | strcmp(antType,'LA'))
%  %error('DBT-Error: Only implemeted for antennaType ULA, LA and elem')
%  dbtwarning('The function "gettap1" only intended for antennaType ULA, LA and elem.')
%end


% ****************** Pick out fields from input parameters. ******************

noElem  = antenna.noElem; % Number of channels.

% ----------------------------------------------------------------------- %
% Different taper types.
% ----------------------------------------------------------------------- %

% ----------------------------------------------------------------------- %
%  Taylor according to Fredrik Athley
% ----------------------------------------------------------------------- %
if (strcmp(taperType,'taylor2'))
  %if ((length(taperParam) > 0) & (isempty(taperParam(1)))) % SLL in dB
  %  taperParam(1) = 30;
  %end%if
 [SLL, nbar] = taylorArguments(taperParam,noElem);
 wOut = tayltap(SLL,nbar,noElem).';


% ----------------------------------------------------------------------- %
%  Taylor according to Lars Pettersson.
% ----------------------------------------------------------------------- %
elseif (strcmp(taperType,'taylor'))
  [SLL, nbar] = taylorArguments(taperParam,noElem);
  wOut = taylorlp(noElem,SLL,nbar);
  wOut = wOut(:);


% ----------------------------------------------------------------------- %
%  Dolhp-Chebychev weights.
% ----------------------------------------------------------------------- %
elseif (strcmp(taperType,'cheby'))
  if (isempty(taperParam))    % SLL in dB
    taperParam = 30;
  end%if
  chkdtype(taperParam, 'RealScalarT')
  wOut = chebylp(noElem,taperParam);
  wOut = wOut(:);


% ----------------------------------------------------------------------- %
%  Uniform or 'notaper'
% ----------------------------------------------------------------------- %
elseif (strcmp(taperType,'uniform') | strcmp(taperType,'notaper'))
  wOut = ones(noElem,1);

% ----------------------------------------------------------------------- %
%  User defined taper.
% ----------------------------------------------------------------------- %
elseif (strcmp(taperType,'user'))
  wOut = taperParam;

% ----------------------------------------------------------------------- %
%
% ----------------------------------------------------------------------- %
elseif (strcmp(taperType,'dummy'))

% ----------------------------------------------------------------------- %
%
% ----------------------------------------------------------------------- %

else
  error(['Selected taper type ',taperType,' is not implemented.'])
end%if

% ----------------------------------------------------------------------- %
% Scanning of the main beam.
% ----------------------------------------------------------------------- %

%scanPhases = antenna.elemPos.' * doa2wavevec(scanDoa,wavelength)

%endfunction gettap1



function [SLL, nbar] = taylorArguments(taperParam,noElem)
% Gives default values and checks input parameters for Taylor tapers.
  if (isempty(taperParam(1))) % SLL in dB
    taperParam(1) = 30;
  end%if
  if (length(taperParam) == 1) % nbar
    %taperParam(2) = 12;  % Suitable for 'taylor2' but not for 'taylor'.
    taperParam(2) = fix(noElem/2)-1;
  end%if
 chkdtype(taperParam(1), 'RealScalarT')
 chkdtype(taperParam(2), 'RealScalarT')
 SLL = taperParam(1);
 nbar = taperParam(2);
%endfunction taylorArguments